U.S. patent application number 15/664569 was filed with the patent office on 2018-03-01 for method for eliminating flicker in emergency lighting driver devices during pulse charging.
This patent application is currently assigned to TRIDONIC GMBH & CO KG. The applicant listed for this patent is TRIDONIC GMBH & CO KG. Invention is credited to James Frankland.
Application Number | 20180062425 15/664569 |
Document ID | / |
Family ID | 57139906 |
Filed Date | 2018-03-01 |
United States Patent
Application |
20180062425 |
Kind Code |
A1 |
Frankland; James |
March 1, 2018 |
METHOD FOR ELIMINATING FLICKER IN EMERGENCY LIGHTING DRIVER DEVICES
DURING PULSE CHARGING
Abstract
An emergency lighting driver device is configured to assume an
operation mode in which: the battery is charged by applying the
pulse signal to the transistor from the control unit, while the LED
load is driven, wherein the emergency lighting driver device is
configured to delay the pulse signal such that the rising edge(s)
and/or falling edge(s) of the pulse signal have a transition time
of at least 0.5 seconds, preferably at least 1 second, more
preferred more than 1.5 seconds and preferably less than 3 seconds;
and/or wherein the pulse signal is fed through a low pass filter
unit of the emergency lighting driver device delaying the
transition time of the rising edge(s) and/or falling edge(s) of the
pulse signal before feeding it to the transistor.
Inventors: |
Frankland; James; (Barton,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TRIDONIC GMBH & CO KG |
Dornbirn |
|
AT |
|
|
Assignee: |
TRIDONIC GMBH & CO KG
Dornbirn
AT
|
Family ID: |
57139906 |
Appl. No.: |
15/664569 |
Filed: |
July 31, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 9/06 20130101; H02J
7/0068 20130101; H05B 45/50 20200101; H05B 45/10 20200101; H02J
7/00711 20200101 |
International
Class: |
H02J 9/06 20060101
H02J009/06; H05B 33/08 20060101 H05B033/08; H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2016 |
GB |
1615061.7 |
Claims
1. An emergency lighting driver device (1) for driving a lighting
unit (10) comprising at least one emergency lighting source with a
LED unit comprising at least one LED, wherein the emergency
lighting driver device (1) comprises a) an input terminal (2) being
configured to be supplied with a supply voltage (11), b) a battery
(4) connected in series to a transistor (5), wherein the series
connection (6) of the battery (4) and the transistor (5) is
directly or indirectly connected in parallel to the input terminal
(2), such that the battery (4) is chargeable starting from the
supply voltage (11), c) a LED driver (8) connected in parallel to
the series connection (6) of the battery (4) and the transistor
(5), the LED driver (8) having an output terminal (9) for driving a
LED load (10), and d) a control unit (7) being configured to
feedback-control the current through the LED load (10) by
controlling the LED driver (8) and being configured to apply a
pulse signal to the transistor (5) for controlling the charging of
the battery (4), e) wherein the emergency lighting driver device
(1) is configured to assume an operation mode in which: the battery
(4) is charged by applying the pulse signal to the transistor (5)
from the control unit (7), while the LED load (10) is driven, and
the emergency lighting driver device (1) is configured to delay the
pulse signal such that the rising edge(s) and/or falling edge(s) of
the pulse signal have a transition time of at least 0.5
seconds.
2. An emergency lighting driver device (1) according to claim 1,
wherein the emergency lighting driver device (1) comprises a low
pass filter unit (12) configured to delay the transition time of
the rising edge(s) and/or falling edge(s) of the pulse signal
before feeding it to the transistor (5).
3. An emergency lighting driver device (1) for driving a lighting
unit (10) comprising at least one emergency lighting source with a
LED unit comprising at least one LED, wherein the emergency
lighting driver device (1) comprises a) an input terminal (2) being
configured to be supplied with a supply voltage (11), b) a battery
(4) connected in series to a transistor (5), wherein the series
connection (6) of the battery (4) and the transistor (5) is
directly or indirectly connected in parallel to the input terminal
(2), such that the battery (4) is chargeable starting from the
supply voltage (11), c) a LED driver (8) connected in parallel to
the series connection (6) of the battery (4) and the transistor
(5), the LED driver (8) having an output terminal (9) for driving a
LED load (8), and d) a control unit (7) being configured to
feedback-control the current through the LED load (10) by
controlling the LED driver (8) and being configured to apply a
pulse signal to the transistor (5) for controlling the charging of
the battery (4), e) wherein the emergency lighting driver device
(1) is configured to assume an operation mode in which: the battery
(4) is charged by applying the pulse signal to the transistor (5)
from the control unit (7), while the LED load (10) is driven, and
the pulse signal is fed through a low pass filter unit (12) of the
emergency lighting driver device (1) delaying the transition time
of the rising edge(s) and/or falling edge(s) of the pulse signal
before feeding it to the transistor (5).
4. An emergency lighting driver device (1) according to claim 3,
wherein the low pass filter unit (12) is configured to delay the
pulse signal such that the rising edge(s) and/or falling edge(s) of
the pulse signal have a transition time of at least 0.5
seconds.
5. An emergency lighting driver device (1) according to claim 3,
wherein the low pass filter unit (12) comprises at least one
RC-element (R1, C3).
6. An emergency lighting driver device (1) according to claim 3,
wherein the LED driver (8) comprises at least one switched
converter (S2, L3, D2, C2), and the control unit (7) is configured
to feedback-control the current through the LED load (10) by
adapting the switching of the at least one switched converter (S2,
L3, D2, C2).
7. An emergency lighting driver device (1) according to claim 3,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the current through the LED load
(10) being feedback-controlled by the control unit (7) is within
10% of the nominal value for the current through the LED load
(10).
8. An emergency lighting driver device (1) according to claim 3,
wherein the transistor (5) is a MOSFET and the control unit (7) is
configured to apply the pulse signal to the gate-terminal of the
MOSFET.
9. An emergency lighting driver device (1) according to claim 8,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the MOSFET is driven through its
active region during the transition time of the rising edge(s)
and/or falling edge(s) of the pulse signal.
10. (canceled)
11. An emergency lighting driver device (1) according to claim 3,
wherein for charging the battery (4) the control unit (7) is
configured to control the transistor (5) such that the transistor
(5) is alternately switched between the conducting state and the
non-conducting state, the transistor (5) is in the conducting state
for a predetermined conducting time and in the non-conducting state
for a predetermined non-conducting time, and the predetermined
non-conducting time is longer than the predetermined conducting
time.
12. An emergency lighting driver device (1) according to claim 11,
wherein the predetermined conducting time corresponds to 4 minutes
and the predetermined non-conducting time corresponds to 16
minutes.
13. An emergency lighting driver device (1) according to claim 11,
wherein for charging the battery (4) the control unit (7) is
configured to control the transistor (5) such that the transistor
(5) is in the conducting state for a predetermined initial
conducting time before being alternately switched between the
conducting state and the non-conducting state, and the
predetermined initial conducting time is longer than the
predetermined non-conducting time.
14. An emergency lighting driver device (1) according to claim 13,
wherein the predetermined initial conducting time corresponds to 20
hours.
15. An emergency lighting device comprising an emergency lighting
driver device (1) according to claim 3, and a lighting unit (10)
comprising at least one emergency lighting source with a LED unit
comprising at least one LED, wherein the emergency lighting driver
device (1) is configured to drive the lighting unit (10) starting
from a voltage supply (11) via its input terminal (2) in a normal
operation mode and to drive the lighting unit (10) starting from
the battery (4) in an emergency operation mode.
16. (canceled)
17. (canceled)
18. An emergency lighting driver device (1) according to claim 1,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the rising edge(s) and/or falling
edge(s) of the pulse signal have a transition time of at least 1.0
seconds and less than 3 seconds.
19. An emergency lighting driver device (1) according to claim 3,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the rising edge(s) and/or falling
edge(s) of the pulse signal have a transition time of at least 1.0
seconds and less than 3 seconds.
20. An emergency lighting driver device (1) according to claim 2,
wherein the low pass filter unit (12) comprises at least one
RC-element (R1, C3).
21. An emergency lighting driver device (1) according to claim 1,
wherein the LED driver (8) comprises at least one switched
converter (S2, L3, D2, C2), and the control unit (7) is configured
to feedback-control the current through the LED load (10) by
adapting the switching of the at least one switched converter (S2,
L3, D2, C2).
22. An emergency lighting driver device (1) according to claim 1,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the current through the LED load
(10) being feedback-controlled by the control unit (7) is within
10% of the nominal value for the current through the LED load
(10).
23. An emergency lighting driver device (1) according to claim 1,
wherein the transistor (5) is a MOSFET and the control unit (7) is
configured to apply the pulse signal to the gate-terminal of the
MOSFET.
24. An emergency lighting driver device (1) according to claim 8,
wherein the emergency lighting driver device (1) is configured to
delay the pulse signal such that the MOSFET is driven through its
active region during the transition time of the rising edge(s)
and/or falling edge(s) of the pulse signal.
25. An emergency lighting driver device (1) according to claim 1,
wherein for charging the battery (4) the control unit (7) is
configured to control the transistor (5) such that the transistor
(5) is alternately switched between the conducting state and the
non-conducting state, the transistor (5) is in the conducting state
for a predetermined conducting time and in the non-conducting state
for a predetermined non-conducting time, and the predetermined
non-conducting time is longer than the predetermined conducting
time.
26. An emergency lighting driver device (1) according to claim 25,
wherein the predetermined conducting time corresponds to 4 minutes
and the predetermined non-conducting time corresponds to 16
minutes.
27. An emergency lighting driver device (1) according to claim 25,
wherein for charging the battery (4) the control unit (7) is
configured to control the transistor (5) such that the transistor
(5) is in the conducting state for a predetermined initial
conducting time before being alternately switched between the
conducting state and the non-conducting state, and the
predetermined initial conducting time is longer than the
predetermined non-conducting time.
28. An emergency lighting driver device (1) according to claim 27,
wherein the predetermined initial conducting time corresponds to 20
hours.
29. An emergency lighting device comprising an emergency lighting
driver device (1) according to claim 1, and a lighting unit (10)
comprising at least one emergency lighting source with a LED unit
comprising at least one LED, wherein the emergency lighting driver
device (1) is configured to drive the lighting unit (10) starting
from a voltage supply (11) via its input terminal (2) in a normal
operation mode and to drive the lighting unit (10) starting from
the battery (4) in an emergency operation mode.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to emergency lighting driver
devices for driving a lighting unit comprising at least one
emergency lighting source, in particular to emergency lighting
driver devices for driving a LED unit comprising at least one LED.
The invention further relates to an emergency lighting device
comprising one of such emergency lighting driver devices and a
lighting unit comprising at least one emergency lighting source,
preferably a LED unit comprising at least one LED, as well as to
methods for charging the battery of such emergency lighting driver
devices.
TECHNICAL BACKGROUND
[0002] In the prior art emergency lighting driver devices for
driving a lighting unit with at least one emergency lighting
source, in particular a LED unit with at least one LED, are well
known.
[0003] In complex lighting systems, such as the lighting system in
a large building, emergency lighting driver devices are vital in
order to provide emergency lighting in case the normal electrical
energy supply of the lighting system, such as e.g. mains, is
disturbed or interrupted. That is, in case of emergency event, such
an emergency lighting driver device is configured to provide an
emergency lighting, wherein the emergency lighting driving device
comprises a battery for driving a lighting unit comprising at least
one emergency lighting source in the emergency operation mode. An
emergency event is for example a black-out caused by the public
utility company or a fire which disturbs or interrupts the normal
electrical energy supply. The emergency lighting driver device is
configured to monitor the normal electrical energy supply, in order
to drive the lighting unit with at least one emergency lighting
source in the emergency operation mode upon detecting a drop in the
electrical energy or voltage of the normal electrical energy
supply. During the normal operation mode, i.e. when the normal
electrical energy supply is working, the emergency lighting driver
device does not drive the lighting unit with the at least one
emergency lighting source. The emergency lighting driver unit may
charge its battery in the normal operation mode.
[0004] Specific emergency lighting driver devices are known which
are configured to drive the lighting unit, in addition to the
battery-driven emergency operation mode, in the normal operation
mode, wherein the electrical energy for driving the lighting unit
comes from a mains voltage.
[0005] The battery of the emergency lighting driver device must be
charged during the normal operation mode with electrical energy
from the normal electrical energy source, i.e. mains, in order to
be able to provide electrical energy for driving the lighting unit
during the emergency operation mode.
[0006] The battery of an emergency lighting driver device is
typically charged during the normal operation mode. For charging
the battery a pulse charge method may be used, i.e. the battery is
alternately charged for a certain time period and then not charged
for a certain time period. To implement such a pulse charging, the
battery is alternately connected and disconnected from the supply
with electrical energy starting from the normal electrical energy
source, wherein the battery is charged with electrical energy when
being connected to the normal electrical energy source and not
charged when being disconnected.
[0007] Usually this is achieved by connecting a switch in series to
the battery, wherein the series connection of the battery and the
switch is in parallel to the normal electrical energy source. For
performing the pulse charge method the switch is then controlled
using a pulse signal, wherein e.g. the switch is turned on, i.e.
switched to the conducting state, as a result of a rising edge of
the pulse signal and turned off, i.e. switched to the
non-conducting state, as a result of a falling edge of the pulse
signal. When the switch is in the conducting state, the battery is
charged with electrical energy from the normal electrical energy
source and when the switch is in the non-conducting state the
battery is not charged with electrical energy. The pulse charge
method is preferred for charging nickel-metal hydride batteries
(NiMh).
[0008] The present invention is now concerned with a further
specific type of emergency lighting driver devices that are
configured [0009] to drive a lighting unit with at least one
emergency lighting source with the electrical energy stored in its
battery in the emergency operation mode, [0010] to drive the
lighting unit with electrical energy provided from the normal
electrical energy source, e.g. mains, in the normal operation mode,
and [0011] to charge its battery with electrical energy provided
from the normal electrical energy source, while driving the
lighting unit with electrical energy provided from the normal
electrical energy source, in the normal operation mode.
[0012] When such an emergency lighting driver device according to
the state of the art drives a LED load during the normal operation
mode, while the battery of the emergency lighting driver is being
pulse charged, the light emitted by the LED load may show a
flicker, i.e. a visible fluctuation in the intensity of the light
emitted by the LED load.
[0013] Namely, due to the connecting and disconnecting of the
battery to respectively from the normal electrical energy source as
a result of switching the switch in series to the battery during
the pulse charging, the electrical energy, in particular the
current, that is supplied to the LED load may rapidly increase,
i.e. overshoot, or rapidly decrease, i.e. undershoot, causing the
flicker.
[0014] Even in case a LED driver is present in the emergency
lighting driver device for feedback-controlling the current flowing
through the LED load, the flicker occurs, as the feedback control
is typically too slow in order to react to the overshooting or
undershooting caused by the connecting and disconnecting of the
battery to respectively from the normal electrical energy
source.
[0015] Therefore, it is an object of the present invention to
provide an emergency lighting driver device that is configured to
pulse charge its battery during the normal operation mode, while
driving a LED load at the same time, such that the light emitted by
the LED load does not show a flicker or respectively the flicker of
the emitted light is reduced. In other words, it is an object of
the present invention to overcome the above described problem when
pulse charging the battery of an emergency lighting driver device
during the normal operation mode, while a LED load is driven by the
emergency lighting driver device.
[0016] This and other objects, which become apparent upon reading
the following description, are solved by the invention.
SUMMARY OF THE INVENTION
[0017] According to a first preferred alternative of the present
invention, an emergency lighting driver device for driving a
lighting unit comprising at least one emergency lighting source,
preferably a LED unit comprising at least one LED, is provided,
wherein the emergency lighting driver device comprises: an input
terminal being configured to be supplied with a supply voltage; a
battery connected in series to a transistor, wherein the series
connection of the battery and the transistor is directly or
indirectly connected in parallel to the input terminal, such that
the battery is chargeable starting from the supply voltage; a LED
driver connected in parallel to the series connection of the
battery and the transistor, the LED driver having an output
terminal for driving a LED load; and a control unit being
configured to feedback-control the current through the LED load by
controlling the LED driver and being configured to apply a pulse
signal to the transistor for controlling the charging of the
battery. The emergency lighting driver device according to the
first alternative of the present invention is configured to assume
an operation mode in which: the battery is charged by applying the
pulse signal to the transistor from the control unit, while the LED
load is driven; and the emergency lighting driver device is
configured to delay the pulse signal such that the rising edge(s)
and/or falling edge(s) of the pulse signal have a transition time
of at least 0.5 seconds, preferably at least 1 second, more
preferred more than 1.5 seconds and preferably less than 3
seconds.
[0018] In other words, according to the first preferred alternative
of the present invention, the emergency lighting driver device is
configured to charge its battery, while driving a LED load, and to
delay the pulse signal for controlling the charging of the battery,
in particular for controlling the switching of the transistor, such
that the rising edge(s) and/or the falling edge(s) of the pulse
signal have a transition time of at least 0.5 second, preferably at
least 1 second, more preferred more than 1.5 seconds and preferably
less than 3 seconds.
[0019] Due to the delaying of the pulse signal such that the rising
edge(s) and/or falling edge(s) of the pulse signal have a
transition time of at least 0.5 second, preferably at least 1
second, more preferred more than 1.5 seconds and preferably less
than 3 seconds, the transistor is not suddenly or rapidly switched
on respectively off. That is, when the transistor is switched from
the conducting state to the non-conducting state, the conductivity
of the transistor is slowly decreased during the transition time of
the respective falling or rising edge. When the transistor is
switched from the non-conducting state to the conducting state, the
conductivity of the transistor is slowly increased during the
transition time of the respective rising or falling edge. Thus, the
switching of the transistor does not cause the voltage at the input
terminal, which is used for driving the LED load while charging the
battery, to rapidly increase respectively decrease. As a result,
the feedback-control of the current through the LED load, in view
of its response time, is able to adapt to the changing voltage
level of the voltage at the input terminal caused by the pulse
signal for charging the battery. Therefore, the emergency lighting
driver device according to the first alternative of the present
invention may reduce or prevent flicker of the light emitted by the
LED load.
[0020] Depending on the type of the transistor, the rising edge(s)
may turn the transistor on and the falling edge(s) may turn the
transistor off or the rising edge(s) may turn the transistor off
and the falling edge(s) may turn the transistor on.
[0021] In the context of the present invention, the term "emergency
lighting driver device" is a lighting driver device that is
configured [0022] to drive the lighting unit comprising at least
one emergency lighting source with the electrical energy stored in
its battery in the emergency operation mode, [0023] to drive the
lighting unit with electrical energy provided to its input terminal
from the normal electrical energy source, e.g. mains, in the normal
operation mode, and [0024] to charge its battery with electrical
energy provided to its input terminal from the normal electrical
energy source, while driving the lighting unit with the electrical
energy provided to its input from the normal electrical energy
source, in the normal operation mode.
[0025] The emergency lighting driver device may also charge its
battery in the normal operation mode, without driving the lighting
unit at the same time.
[0026] The normal operation mode preferably corresponds to the
operation mode, when the emergency lighting driver device is
supplied via its input terminal with electrical energy from a
normal electrical energy source, such as e.g. mains or an
electrical energy supply bus. The emergency operation mode
preferably corresponds to the operation mode, when the emergency
lighting driver device drives the lighting unit with electrical
energy stored in its battery, as no or not sufficient electrical
energy for driving the lighting unit is supplied via the input
terminal to the emergency lighting driver device from the normal
electrical energy source due to an emergency event. An example for
an emergency event may be a fire disturbing or interrupting the
normal electrical energy source or an interruption of the normal
electrical energy source due to a black-out caused by the public
utility company.
[0027] Preferably, the emergency lighting driver device is
configured to start the emergency operation mode as a result of
detecting a drop in the electrical energy respectively voltage
supplied from the normal electrical energy source to its input
terminal.
[0028] During the normal operation mode the emergency lighting
driving device drives the lighting unit with electrical energy from
the normal electrical energy source, e.g. mains, and during the
emergency operation mode the emergency lighting driver device
drives the lighting unit with electrical energy from its
battery.
[0029] The supply voltage is preferably supplied to the first
terminal of the emergency lighting driver device from a normal
electrical energy source respectively normal voltage source, such
as mains.
[0030] The series connection of the battery and the transistor is
preferably indirectly connected in parallel to the input terminal
via a driver circuit that is configured to convert the supply
voltage supplied to the input terminal into a voltage for charging
the battery. Preferably, the driver circuit comprises at least one
switched converter that is configured to convert the supply voltage
into a voltage for charging the battery.
[0031] Preferably, such a switched converter corresponds to a
converter with a galvanic isolation, such as flyback-converter,
push-pull-converter, resonant converter etc., or a converter
without a galvanic isolation, such as a buck-converter,
boost-converter, buck-boost-converter etc.
[0032] Preferably, the LED load corresponds to at least one
LED.
[0033] The control unit is preferably a microcontroller, an ASIC or
a hybrid thereof.
[0034] Preferably, the control unit is configured to delay the
pulse signal such that the rising edge(s) and/or falling edge(s) of
the pulse signal have a transition time of at least 0.5 seconds,
preferably at least 1 second, more preferred more than 1.5 seconds
and preferably less than 3 seconds.
[0035] Preferably, the LED driver is any circuit, such as e.g. a
switched converter or a linear regulator circuit, that is
controllable by the control unit for driving a LED load.
[0036] According to the present invention the "feedback-control of
the current through the LED load" may be carried out by any method
known to the skilled person. The emergency lighting driver device
may comprise the means, such as e.g. a shunt resistor for detecting
the current fed to the LED load, for carrying out such a
feedback-control and/or may receive the information needed
therefore from extern.
[0037] In the context of the present invention, the term "pulse
signal" is a signal with one pulse or a plurality of consecutive
pulses, wherein each pulse of the pulse signal comprises a rising
edge and a falling edge. Preferably, the emergency lighting driver
device is configured to delay the pulse signal such that the rising
edge and/or falling edge of at least one pulse of the pulse signal
has a transition time of at least 0.5 seconds, preferably at least
1 second, more preferred more than 1.5 seconds and preferably less
than 3 seconds.
[0038] Preferably, the emergency lighting driver device is
configured to delay the pulse signal such that the rising edge
and/or falling edge of each pulse has a transition time of at least
0.5 seconds, preferably at least 1 second, more preferred more than
1.5 seconds and preferably less than 3 seconds. However, the term
"each pulse" has to be understood as "substantially each pulse",
i.e. it is possible that one or more of the pulses of the pulse
signal are outliers having a different transition time for the
rising edge and/or falling edge.
[0039] In the context of the present invention, a "pulse"
corresponds to a control signal that is able to switch a
transistor, preferably control signal with a substantially vertical
(when seen on the time axis) rising edge and a falling edge.
[0040] For describing the present invention, it is assumed that the
rising edge of the pulse turns the transistor on, i.e. switches the
transistor into the conducting state, and the falling edge of the
pulse turns the transistor off, i.e. switches the transistor into
the non-conducting state. However, as mentioned already above, it
depends on the transistor type whether the rising edge of the pulse
turns the transistor on and the falling edge turns the transistor
off or the rising edge of the pulse turns the transistor off and
the falling edge turns the transistor on.
[0041] Preferably, the pulses of the pulse signal have the same
amplitude and pulse duration. However, the pulses of the pulse
signal may also have different amplitudes and/or pulse durations.
Preferably the time respectively duration between the pulses of the
pulse signal is different to the pulse duration of the pulses.
[0042] Furthermore, the emergency lighting driver device is
preferably configured to charge the battery during the normal
operation mode starting from the supply voltage supplied from a
normal electrical energy source, such as mains, to the input
terminal of the emergency lighting driver device.
[0043] For charging the battery the control unit is preferably
configured to control the switching of the transistor by applying a
pulse signal to the transistor.
[0044] When the transistor is in the conducting state, then the
battery is charged starting from the supply voltage supplied to the
input terminal of the emergency lighting driver device, and when
the transistor is in the non-conducting state, the battery is not
charged.
[0045] Preferably, the emergency lighting driver device according
to the first preferred alternative of the present invention
comprises a low pass filter unit configured to delay the transition
time of the rising edge(s) and/or falling edge(s) of the pulse
signal before feeding it to the transistor.
[0046] Preferably, the control unit comprises the low pass filter
unit that is configured to delay the transition time of the rising
edge(s) and/or falling edge(s) of the pulse signal before feeding
it to the transistor.
[0047] According to a second preferred alternative of the present
invention an emergency lighting driver device for driving a
lighting unit comprising at least one emergency lighting source,
preferably a LED unit comprising at least one LED, is provided,
wherein the emergency lighting driver device comprises an input
terminal being configured to be supplied with a supply voltage; a
battery connected in series to a transistor, wherein the series
connection of the battery and the transistor is directly or
indirectly connected in parallel to the input terminal, such that
the battery is chargeable starting from the supply voltage; a LED
driver connected in parallel to the series connection of the
battery and the transistor, the LED driver having an output
terminal for driving a LED load; and a control unit being
configured to feedback-control the current through the LED load by
controlling the LED driver and being configured to apply a pulse
signal to the transistor for controlling the charging of the
battery. The emergency lighting driver device according to the
second preferred alternative of the present invention is configured
to assume an operation mode in which: the battery is charged by
applying the pulse signal to the transistor from the control unit,
while the LED load is driven; and the pulse signal is fed through a
low pass filter unit of the emergency lighting driver device
delaying the transition time of the rising edge(s) and/or falling
edge(s) of the pulse signal before feeding it to the
transistor.
[0048] In other words, according to the second preferred
alternative of the present invention, the emergency lighting driver
device comprises a low pass filter unit that is configured to delay
the transition time of the rising edge(s) and/or the falling
edge(s) of the pulse signal for controlling the charging of the
battery, in particular for controlling the switching of the
transistor, before the pulse signal is fed to the transistor.
[0049] Due to the delaying of the transition time of the rising
edge(s) and/or falling edge(s) of the pulse signal, before feeding
the pulse signal to the transistor, the transistor is not suddenly
or rapidly switched on respectively off. That is, when the
transistor is switched from the conducting state to the
non-conducting state, the conductivity of the transistor is slowly
decreased during the transition time of the respective rising or
falling edge. When the transistor is switched from the
non-conducting state to the conducting state, the conductivity of
the transistor is slowly increased during the transition time of
the respective rising or falling edge. Thus, the switching of the
transistor does not cause the voltage at the input terminal, which
is used for driving the LED load while charging the battery, to
rapidly increase respectively decrease. As a result, in view of its
response time, the feedback-control of the current through the LED
load is able to adapt to the changing voltage level of the voltage
at the input terminal caused by the pulse signal for charging the
battery. Therefore, the emergency lighting driver device according
to the second alternative of the present invention may reduce or
prevent flicker of the light emitted by the LED load.
[0050] Preferably, the control unit comprises the low pass filter
unit that is configured to delay the transition time of the rising
edge(s) and/or falling edge(s) of the pulse signal before feeding
it to the transistor.
[0051] Preferably, the low pass filter unit of the emergency
lighting driver device according to the second preferred
alternative of the present invention is configured to delay the
pulse signal such that the rising edge(s) and/or falling edge(s) of
the pulse signal have a transition time of at least 0.5 seconds,
preferably at least 1 second, more preferred more than 1.5 seconds
and preferably less than 3 seconds.
[0052] The following optional features are applicable for both,
above described, alternatives of the present invention:
[0053] Preferably, the low pass filter unit comprises at least one
RC-element.
[0054] Further, the LED driver preferably comprises at least one
switched converter, and the control unit is preferably configured
to feedback-control the current through the LED load by adapting
the switching of the at least one switched converter.
[0055] In other words, the LED driver comprises at least one
converter with at least one switch, wherein the current through the
LED load may be feedback-controlled to a nominal value by
controlling the switching of the at least one switch. Preferably,
the LED driver comprises one switched converter.
[0056] Preferably, the at least one switched converter corresponds
to a converter with a galvanic isolation, such as
flyback-converter, push-pull-converter, resonant converter etc., or
a converter without a galvanic isolation, such as a buck-converter,
boost-converter, buck-boost-converter etc.
[0057] Furthermore, the emergency lighting driver device is
preferably configured to delay the pulse signal (and to have a
feedback control with a matched time response) such that the
current through the LED load, being feedback-controlled by the
control unit, is within 30%, preferably 20%, more preferred 10%,
even more preferred 5% of the nominal value for the current through
the LED load.
[0058] Moreover, the transistor is preferably a MOSFET and the
control unit is preferably configured to apply the pulse signal to
the gate-terminal of the MOSFET.
[0059] The transistor may also be another transistor type, such as
e.g. a bipolar transistor.
[0060] Preferably, the emergency lighting driver device is
configured to delay the pulse signal such that the MOSFET is driven
through its active region during the transition time of the rising
edge(s) and/or falling edge(s) of the pulse signal.
[0061] That is, preferably, when the MOSFET is switched from the
conducting state to the non-conducting state, the MOSFET drives
through its active region during the transition time of the
respective rising or falling edge, wherein the conductivity of the
MOSFET decreases as the MOSFET drives through its active region.
Preferably, when the MOSFET is switched from the non-conducting
state to the conducting state, the MOSFET drives through its active
region during the transition time of the respective rising or
falling edge, wherein the conductivity of the MOSFET increases as
the MOSFET drives through its active region.
[0062] Further, for charging the battery the control unit is
preferably configured to control the transistor according to a
pulse charge method.
[0063] Preferably, for charging the battery the control unit is
configured to control the transistor such that the transistor is
alternately switched between the conducting state and the
non-conducting state; the transistor is in the conducting state for
a predetermined conducting time and in the non-conducting state for
a predetermined non-conducting time; and the predetermined
non-conducting time is longer than the predetermined conducting
time.
[0064] As described already above, when the transistor is in the
conducting state then the battery is charged with electrical energy
starting from the supply voltage supplied to the input terminal of
the emergency lighting driver device. When the transistor is in the
non-conducting state the battery is not charged with electrical
energy.
[0065] Preferably, the predetermined conducting time corresponds to
2 to 6 minutes, preferably 3 to 5 minutes and the predetermined
non-conducting time corresponds to 10 to 25 minutes, preferably 13
to 19 minutes.
[0066] Preferably, for charging the battery the control unit is
configured to control the transistor such that the transistor is in
the conducting state for a predetermined initial conducting time
before being alternately switched between the conducting state and
the non-conducting state; and the predetermined initial conducting
time is longer than the predetermined non-conducting time.
[0067] The predetermined initial conducting time preferably
corresponds to 15 to 25 hours.
[0068] Furthermore, according to the present invention an emergency
lighting device is provided, wherein the emergency lighting device
comprises an emergency lighting driver device according to the
present invention, as described above, and a lighting unit
comprising at least one emergency lighting source, preferably a LED
unit comprising at least one LED. The emergency lighting driver
device is configured to drive the lighting unit starting from a
voltage supply via its input terminal in a normal operation mode
and to drive the lighting unit starting from the battery in an
emergency operation mode.
[0069] Moreover, according to the present invention a method for
charging the battery of an emergency lighting driver device
according to the present invention, as described above, is
provided; wherein the battery is charged by applying the pulse
signal to the transistor from the control unit, while the LED load
is driven, and the emergency lighting driver device delays the
pulse signal such that the rising edge(s) and/or falling edge(s) of
the pulse signal have a transition time of at least 0.5 seconds,
preferably at least 1 second, more preferred more than 1.5 seconds
and preferably less than 3 seconds.
[0070] In addition, according to the present invention a further
method for charging the battery of an emergency lighting driver
device according to the present invention, as described above, is
provided; wherein the battery is charged by applying the pulse
signal to the transistor from the control unit, while the LED load
is driven, and the pulse signal is fed through a low pass filter
unit of the emergency lighting driver device delaying the
transition time of the rising edge(s) and/or falling edge(s) of the
pulse signal before feeding it to the transistor.
[0071] According to the present invention, the above optional
features may be arbitrarily combined.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] In the following, the invention is described exemplarily
with reference to the enclosed figures. The figures merely show
preferred embodiments of the present invention. Same elements in
the figures are referenced by same reference signs. In detail,
[0073] FIG. 1 is a schematic view of a circuit diagram of an
emergency lighting driver device according to a preferred
embodiment of the invention;
[0074] FIG. 2 is a further schematic view of a circuit diagram of
an emergency lighting driver device according to the preferred
embodiment of the invention shown in FIG. 1, wherein the schematic
view of FIG. 2 is more detailed in comparison to the schematic view
of FIG. 1;
[0075] FIG. 3 is a schematic view of a circuit diagram of an
emergency lighting driver device according to a further preferred
embodiment of the invention; and
[0076] FIG. 4 is a further schematic view of a circuit diagram of
an emergency lighting driver device according to the preferred
embodiment of the invention shown in FIG. 3, wherein the schematic
view of FIG. 4 is more detailed in comparison to the schematic view
of FIG. 3.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0077] FIG. 1 is a schematic view of a circuit diagram of an
emergency lighting driver device according to a preferred
embodiment of the invention.
[0078] The emergency lighting driver device 1, shown in FIG. 1,
comprises an input terminal 2, a driver circuit 3, a series
connection 6 of a battery 4 and a transistor 5, a control unit 7
and a LED driver 8. The series connection 6 of the battery 4 and
the transistor 5 is indirectly connected via the driver circuit 3
in parallel to the input terminal 2. Preferably, the series
connection 6 of the battery 4 and the transistor 5 may also be
directly connected in parallel to the input terminal 2 (not shown
in FIG. 1). That is, the emergency lighting driver device may not
comprise the driver circuit 3.
[0079] The LED driver 8 is connected in parallel to the series
connection 6 of the battery 4 and the transistor 5.
[0080] The LED driver 8 is configured to drive via its output
terminal 9 a LED load 10, which may be a lighting unit 10 with at
least one emergency lighting source, in particular a LED unit
comprising at least one LED. That is, the emergency lighting driver
device 1 is configured to drive the lighting unit 10 comprising at
least one emergency lighting source, preferably a LED unit
comprising at least one LED.
[0081] The emergency lighting driver device 1 and the lighting unit
10 may form together an emergency lighting device.
[0082] The emergency lighting driver device 1 is configured to
drive the lighting unit 10 with electrical energy provided by a
normal energy source 11 respectively voltage source, such as mains,
or provided by the battery 4. As mentioned already above, the
operation mode when the emergency lighting driver device 1 is
supplied with electrical energy via its input terminal 2 from a
normal energy source 11 for driving the lighting unit 10 is called
normal operation mode. The operation mode when the emergency
lighting driver device 1 is not supplied with electrical energy via
its input terminal 2 or is not supplied with sufficient electrical
energy for driving the lighting unit 10 is called emergency
operation mode. In the emergency operation mode the electrical
energy stored in the battery 4 is used for driving the lighting
unit 10, in particular the at least one emergency lighting
source.
[0083] The driver circuit 3 is configured to convert the voltage
supplied to the input terminal 2 of the emergency lighting driver
device 1 into a voltage suitable for charging the battery 4.
[0084] The LED driver 8 comprises an output terminal 9 for driving
a LED load, such as the lighting unit 10. The LED driver 8
preferably comprises at least one switched converter configured to
provide the electrical energy, in particular the current, for
driving the lighting unit 10. The LED driver 8 is preferably
controllable by the control unit 7 in order to drive the lighting
unit 10 starting from the output voltage of the driving circuit 3
(during the normal operation mode and in case the driving circuit 3
is present), the voltage at the input terminal 2 (during the normal
operation mode and in case the driving circuit 3 is not present) or
the voltage provided by the battery 4 (during the emergency
operation mode).
[0085] The control unit 7 is preferably configured to control the
driver circuit 3, the switching of the transistor 5 and the LED
driver 8.
[0086] In particular, the control unit 7 is preferably configured
to control the conversion of the voltage at the input terminal 2 by
the driver circuit 3 into a voltage at the output of the driver
circuit 3, which is suitable for charging the battery and/or
driving the lighting unit 10.
[0087] The control unit 7 is preferably configured to
feedback-control the current flowing through the lighting unit 10
representing a LED load by controlling the LED driver 8. In case
the LED driver 8 comprises at least one switched converter, the
control unit is configured to feedback-control the current through
the LED load 10 by adapting respectively controlling the switching
of the at least one switched converter.
[0088] The control unit 7 is configured to control the switching of
the transistor 5 by applying a pulse signal to the transistor 5 in
order to control the charging of the battery 4. In case the
transistor 5 is turned off, i.e. in the non-conducting state, the
battery 4 is not charged with electrical energy. In case the
transistor 5 is turned on, i.e. in the conducting state, the
battery 4 is charged with electrical energy starting from the
output voltage of the driving circuit 3 (during the normal
operation mode and in case the driving circuit 3 is present) or the
voltage at the input terminal 2 (during the normal operation mode
and in case the driving circuit 3 is not present).
[0089] The emergency lighting driver device 1, preferably the
control unit 7, is configured to delay the pulse signal such that
the rising edge(s) and/or falling edge(s) of the pulse signal have
a transition time of at least 0.5 seconds, preferably at least 1
second, more preferred more than 1.5 seconds and preferably less
than 3 seconds.
[0090] Preferably the control unit 7 comprises a low pass filter
unit (not shown in FIG. 1) that is configured to delay the
transition time of the rising edge(s) and/or falling edge(s) of the
pulse signal before feeding it to the transistor 5.
[0091] FIG. 2 is a further schematic view of a circuit diagram of
an emergency lighting driver device according to the preferred
embodiment of the invention shown in FIG. 1, wherein the schematic
view of FIG. 2 is more detailed in comparison to the schematic view
of FIG. 1.
[0092] The emergency lighting driver device 1 shown in FIG. 2
substantially corresponds to the emergency lighting driver device 1
shown in FIG. 1, wherein the driver circuit 3, the transistor 5 and
the LED driver 8 are shown in more detail.
[0093] The driver circuit 3 comprises a flyback-converter that
provides a galvanic isolation between the input terminal 2 and the
series connection 6 of the battery 4 and the transistor 5. As
already mentioned above, the driver circuit 3 may be implemented
differently or may be fully omitted, such that the series
connection 6 of the battery 4 and the transistor 5 is directly
connected in parallel to the input terminal 2.
[0094] The flyback-converter of the driver circuit 3 comprises a
switch S1, a transformer with the primary winding L1 and the
secondary winding L2, a diode D1 and a capacitor C1. The control
unit 7 is preferably configured to control the voltage provided at
the capacitor C1 starting from the voltage at the input terminal 2,
i.e. control the conversion of the voltage at the input terminal 2
to the voltage at the capacitor C1.
[0095] The LED driver 8 comprises one switched converter in the
form of a buck-boost converter. As already mentioned above, the LED
driver may be implemented differently.
[0096] The buck-boost converter comprises a switch S2, an inductor
L1, a diode D2 and a capacitor C2. The control unit 7 is configured
to control the switching of the switch S2 in order to
feedback-control the current through the lighting unit 10,
representing a LED load. The means needed besides the switch S2 for
feedback-controlling the current trough the lighting unit 10 are
not shown in FIG. 2.
[0097] The transistor 5 corresponds to a MOSFET
(metal-oxide-semiconductor field-effect-transistor), wherein the
control unit 7 is configured to apply the pulse signal for
controlling the charging of the battery 4 to the gate-terminal of
the MOSFET. As already mentioned above, the transistor 5 may also
be implemented differently.
[0098] FIG. 3 is a schematic view of a circuit diagram of an
emergency lighting driver device according to a further preferred
embodiment of the invention.
[0099] The emergency lighting driver device 1 shown in FIG. 3
substantially corresponds to the emergency lighting driver device 1
shown in FIG. 1. Thus, the description with respect to FIG. 1 is
also valid for the emergency lighting driver device shown in FIG. 3
and in the following merely the differences between these two
preferred embodiments will be described.
[0100] With respect to the emergency lighting driver device 1
according to the preferred embodiment shown in FIG. 1, the
emergency lighting driver device 1 according to the preferred
embodiment shown in FIG. 3 additionally comprises a low pass filter
unit 12.
[0101] The low pass filter unit 12 is configured to delay the
transition time of the rising edge(s) and/or falling edge(s) of the
pulse signal, provided from the control unit 7 for controlling the
transistor, before feeding the pulse signal to the transistor
5.
[0102] Preferably, the low pass filter unit 12 is configured to
delay the pulse signal such that the rising edge(s) and/or falling
edge(s) of the pulse signal have a transition time of at least 0.5
seconds, preferably at least 1 second, more preferred more than 1.5
seconds and preferably less than 3 seconds.
[0103] FIG. 4 is a further schematic view of a circuit diagram of
an emergency lighting driver device according to the preferred
embodiment of the invention shown in FIG. 3, wherein the schematic
view of FIG. 4 is more detailed in comparison to the schematic view
of FIG. 3.
[0104] The emergency lighting driver device 1 shown in FIG. 4
substantially corresponds to the emergency lighting driver device
shown in FIG. 3, wherein the driver circuit 3, the transistor 5,
the LED driver 8 and the low pass filter unit 12 are shown in more
detail.
[0105] The driver circuit 3, the transistor 5 and the LED driver 8
of the emergency lighting driver unit 1 of FIG. 4 are implemented
in the same way as the driver circuit 3, the transistor 5 and the
LED driver 8 of the emergency lighting driver unit 1 of FIG. 2.
Thus, please refer to the corresponding description of FIG. 2 with
respect to the implementation of the driver circuit 3, the
transistor 5 and the LED driver 8 of the emergency lighting driver
unit 1 of FIG. 4.
[0106] The low pass filter unit 12 shown in FIG. 4 comprises a
RC-element with one resistor R1 and one capacitor C3. The low pass
filter unit 12 may also be implemented differently. For example the
low pass filter unit 12 may also comprise more than one
RC-element.
[0107] To sum up, the present invention focuses on describing an
advantageous emergency lighting driver device compared to the state
of the art that is configured to charge its battery during the
normal operation mode, while driving a LED load at the same time.
In particular, the present invention focuses on describing the
control of the charging of the battery using a pulse signal for
performing a pulse charging. Thus, the feedback-control of the
current through the LED load by the LED driver of the emergency
lighting driver device and the voltage conversion performed by the
optional driver circuit connected between the input terminal and
the series connection of the battery and the transistor are only
schematically described herein and may be implemented in one way or
another known to the skilled person.
* * * * *